Biomedical subjects

R L Brinster

Publications and source records attributed to R L Brinster.

12 recordsLinked to original sources

PubMed1979

Protein degradation in the mouse blastocyst.

The degradation characteristics of 56 individual newly synthesized proteins of the Day 4 mouse blastocyst have been examined employing double isotope labeling of proteins for half-life measurement and two-dimensional electrophoresis for separation of proteins. The half-lives ranged from 1 to approximately 30 h with a mean of 12.4 h. Several proteins appeared to have half-lives greater than 30 h but decay times were insufficient to provide precise information for these proteins. The results suggest there is a tendency for proteins with acidic isoelectric points to be degraded more rapidly than basic proteins, and for high molecular weight proteins to be degraded more rapidly than low molecular weight proteins. Although the regressions of these two parameters on half-life were not significant, the direction and magnitude of the trends were similar to those previously described for liver proteins. Two specific proteins, tubulin and actin, were tentatively identified, and their half-lives determined. Tubulin had a half-life of 9.0 h. The half-lives of the provisionally identified gamma, beta, and alpha forms of actin were 2.2, 8.7, and 5.4 h respectively.

Actins↗

PubMed1979

Requirements for blastocyst development in vitro.

Four characteristics of culture medium that are important to embryo development and nutrition of the blastocyst have been discussed. An examination of several of the most commonly used media for embryo culture demonstrates many similarities among them. The milliosmolarities of the media range from the hypoosmotic optimums (256 milliosmols) demonstrated in several in vitro studies to the physiologic range (308 to 315 milliosmols). Media between these extremes generally allow good development. Low oxygen concentrations (5%) in the culture environment allow somewhat better development of early cleavage stages, but recent studies suggest the difference between development in 5 and 20% oxygen to be less than originally thought. The media most commonly employed for early embryo culture contain bicarbonate as the buffer, but maintenance of pH is probably not the most crucial role of the CO2-bicarbonate content of the media. Likewise, since 1965 almost all media used to culture embryos have used pyruvate as the primary energy source. This is particularly important when early stages, before blastocyst development, are cultured. The concentration used generally falls within the optimum range of 2.5 to 5.0 X 10(-4)M first reported. Although glucose is not oxidized well by the early cleavage stages, it is an important energy source for all blastocysts. Furthermore, glucose contributes more than any other carbon source, including amino acids, to protein formation. Much is yet to be learned concerning the nutrition of the blastocyst, but our knowledge has increased immensely during the last 15 years. Hopefully our progress will be at least as rapid in the coming decade.

Animals↗

PubMed1978

Effects of alpha-amanitin on RNA synthesis by mouse embryos in culture.

Investigations were conducted to test the effects of alpha-amanitin on RNA synthesis in preimplantation mouse embryos. Exposure of embryos in culture to 1-100 microgram/ml alpha-amanitin produced a dose- and time-dependence suppression of total RNA synthesis as measured by incorporation of [3H]uridine. Synthesis of polyadenylated RNA in blastocyst-stage embryos was abolished by alpha-amanitin-treatment at concentrations and exposure times that suppressed total RNA synthesis by less than 15%. DNA-dependent RNA polymerase activity was measured in lysates of embryos at several stages of preimplantation development. alpha-Amanitin suppressed total polymerase activity assayed under ionic conditions favorable to the detection of RNA polymerase II. Electrophoretic analyses revealed that preincubation of blastocysts in 100 microgram/ml alpha-amanitin reduced labelling of cytoplasmic 28S and 18S RNA by inhibition of both synthesis and maturation of nucleolar 45SrRNA-precursor. This action of alpha-amanitin on nucleolar RNA synthesis cannot be correlated with the minimal suppression of nucleolar RNA polymerase activity and suggests that the synthesis and processing of rRNA may be under control of nucleoplasmic gene products.

Amanitins↗

PubMed1978